Seismic and geodetic evidence for extensive, long-lived fault damage zones
Seismic and geodetic evidence for extensive, long-lived fault damage zones
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DOI：
10.1130/g25306a.1
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发表时间：
2009-04-01
期刊：
影响因子：
5.8
通讯作者：
Vidale, John E.
中科院分区：
文献类型：
--
作者：
Cochran, Elizabeth S.;Li, Yong-Gang;Vidale, John E.
在地震期间，滑动通常局限于预先存在的断层上，但目前尚不清楚地壳断层的结构如何有助于滑动定位和能量学。越来越多的证据表明，沿活动断层的地壳在大地震期间会经历异常应变和损坏。来自加州东部剪切带卡利科断层的地震和大地测量数据揭示了大范围的地震速度和有效弹性模量降低的区域。利用地震走时、陷波和干涉合成孔径雷达观测，我们记录了与卡利科断层沿线 1.5 公里宽区域的围岩相比，地震速度降低了 40%-50%，剪切模量降低了 65%。观察到的速度降低可能代表了过去地震破裂造成的累积机械损伤。历史上没有发生过大地震破坏卡利科断层，这意味着断层破坏会持续数百年甚至数千年。这些发现表明，断层可以影响距主断层滑移面很远的地方以及整个发震带的岩石特性，这一结果对破裂期间驱动岩石开裂和屈服以及断层系统发育所消耗的能量有影响。
During earthquakes, slip is often localized on preexisting faults, but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics. Growing evidence suggests that the crust along active faults undergoes anomalous strain and damage during large earthquakes. Seismic and geodetic data from the Calico fault in the eastern California shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli. Using seismic traveltimes, trapped waves, and interferometric synthetic aperture radar observations, we document seismic velocities reduced by 40%-50% and shear moduli reduced by 65% compared to wall rock in a 1.5-km-wide zone along the Calico fault. Observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures. No large earthquake has broken the Calico fault in historic time, implying that fault damage persists for hundreds or perhaps thousands of years. These findings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces, and throughout much of the seismogenic zone, a result with implications for the amount of energy expended during rupture to drive cracking and yielding of rock and development of fault systems.